[PATCH v2 03/21] drm: Add get_vblank_timestamp() to struct drm_crtc_funcs

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The callback get_vblank_timestamp() is currently located in struct
drm_driver, but really belongs into struct drm_crtc_funcs. Add an
equivalent there. Driver will be converted in separate patches.

The default implementation is drm_calc_vbltimestamp_from_scanoutpos().
The patch adds drm_crtc_vblank_helper_get_vblank_timestamp(), which is
an implementation for the CRTC callback.

v2:
	* rename helper to drm_crtc_vblank_helper_get_vblank_timestamp()
	* replace drm_calc_vbltimestamp_from_scanoutpos() with
	  drm_crtc_vblank_helper_get_vblank_timestamp() in docs

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
 drivers/gpu/drm/drm_vblank.c             | 236 +++++++++++++++++++++--
 include/drm/drm_crtc.h                   |  46 ++++-
 include/drm/drm_modeset_helper_vtables.h |   4 +-
 include/drm/drm_vblank.h                 |  26 ++-
 4 files changed, 292 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index abb085c67d82..1b7af316e6a5 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -333,7 +333,9 @@ u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc)
 	u64 vblank;
 	unsigned long flags;
 
-	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) && !dev->driver->get_vblank_timestamp,
+	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) &&
+		  !crtc->funcs->get_vblank_timestamp &&
+		  !dev->driver->get_vblank_timestamp,
 		  "This function requires support for accurate vblank timestamps.");
 
 	spin_lock_irqsave(&dev->vblank_time_lock, flags);
@@ -511,9 +513,9 @@ EXPORT_SYMBOL(drm_crtc_vblank_waitqueue);
  *
  * Calculate and store various constants which are later needed by vblank and
  * swap-completion timestamping, e.g, by
- * drm_calc_vbltimestamp_from_scanoutpos(). They are derived from CRTC's true
- * scanout timing, so they take things like panel scaling or other adjustments
- * into account.
+ * drm_crtc_vblank_helper_get_vblank_timestamp(). They are derived from
+ * CRTC's true scanout timing, so they take things like panel scaling or
+ * other adjustments into account.
  */
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode)
@@ -577,8 +579,9 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
  *
  * Implements calculation of exact vblank timestamps from given drm_display_mode
  * timings and current video scanout position of a CRTC. This can be directly
- * used as the &drm_driver.get_vblank_timestamp implementation of a kms driver
- * if &drm_crtc_helper_funcs.get_scanout_position is implemented.
+ * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
+ * driver if &drm_crtc_helper_funcs.get_scanout_position or
+ * &drm_driver.get_scanout_position is implemented.
  *
  * The current implementation only handles standard video modes. For double scan
  * and interlaced modes the driver is supposed to adjust the hardware mode
@@ -742,15 +745,22 @@ static bool
 drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
 			  ktime_t *tvblank, bool in_vblank_irq)
 {
+	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
 	bool ret = false;
 
 	/* Define requested maximum error on timestamps (nanoseconds). */
 	int max_error = (int) drm_timestamp_precision * 1000;
 
 	/* Query driver if possible and precision timestamping enabled. */
-	if (dev->driver->get_vblank_timestamp && (max_error > 0))
+	if (crtc->funcs->get_vblank_timestamp && (max_error > 0)) {
+		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+
+		ret = crtc->funcs->get_vblank_timestamp(crtc, &max_error,
+							tvblank, in_vblank_irq);
+	} else if (dev->driver->get_vblank_timestamp && (max_error > 0)) {
 		ret = dev->driver->get_vblank_timestamp(dev, pipe, &max_error,
 							tvblank, in_vblank_irq);
+	}
 
 	/* GPU high precision timestamp query unsupported or failed.
 	 * Return current monotonic/gettimeofday timestamp as best estimate.
@@ -1059,11 +1069,19 @@ EXPORT_SYMBOL(drm_crtc_vblank_get);
 
 static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int pipe)
 {
+	struct drm_crtc *crtc;
+
 	if (!dev->vblank_disable_immediate)
 		return false;
-	if (!dev->driver->get_vblank_timestamp)
-		return false;
-	return true;
+
+	crtc = drm_crtc_from_index(dev, pipe);
+	if (crtc && crtc->funcs->get_vblank_timestamp)
+		return true;
+
+	if (dev->driver->get_vblank_timestamp)
+		return true;
+
+	return false;
 }
 
 static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
@@ -1742,9 +1760,11 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 
 static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
 {
+	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
 	struct drm_pending_vblank_event *e, *t;
 	ktime_t now;
 	u64 seq;
+	bool high_prec;
 
 	assert_spin_locked(&dev->event_lock);
 
@@ -1764,8 +1784,10 @@ static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
 		send_vblank_event(dev, e, seq, now);
 	}
 
-	trace_drm_vblank_event(pipe, seq, now,
-			dev->driver->get_vblank_timestamp != NULL);
+	high_prec = crtc->funcs->get_vblank_timestamp ||
+		    dev->driver->get_vblank_timestamp;
+
+	trace_drm_vblank_event(pipe, seq, now, high_prec);
 }
 
 /**
@@ -2020,3 +2042,193 @@ int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data,
 	kfree(e);
 	return ret;
 }
+
+/*
+ * Helpers for struct drm_crtc_funcs
+ */
+
+/**
+ * drm_crtc_vblank_helper_get_vblank_timestamp_internal - precise vblank
+ *                                                        timestamp helper
+ * @dev: DRM device
+ * @pipe: index of CRTC whose vblank timestamp to retrieve
+ * @max_error: Desired maximum allowable error in timestamps (nanosecs)
+ *             On return contains true maximum error of timestamp
+ * @vblank_time: Pointer to time which should receive the timestamp
+ * @in_vblank_irq:
+ *     True when called from drm_crtc_handle_vblank().  Some drivers
+ *     need to apply some workarounds for gpu-specific vblank irq quirks
+ *     if flag is set.
+ * @get_scanout_position:
+ *     Callback function to retrieve the scanout position. See
+ *     @struct drm_crtc_helper_funcs.get_scanout_position.
+ *
+ * Implements calculation of exact vblank timestamps from given drm_display_mode
+ * timings and current video scanout position of a CRTC.
+ *
+ * The current implementation only handles standard video modes. For double scan
+ * and interlaced modes the driver is supposed to adjust the hardware mode
+ * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
+ * match the scanout position reported.
+ *
+ * Note that atomic drivers must call drm_calc_timestamping_constants() before
+ * enabling a CRTC. The atomic helpers already take care of that in
+ * drm_atomic_helper_update_legacy_modeset_state().
+ *
+ * Returns:
+ *
+ * Returns true on success, and false on failure, i.e. when no accurate
+ * timestamp could be acquired.
+ */
+bool
+drm_crtc_vblank_helper_get_vblank_timestamp_internal(
+	struct drm_crtc *crtc, int *max_error, ktime_t *vblank_time,
+	bool in_vblank_irq,
+	bool (*get_scanout_position)(struct drm_crtc *crtc,
+                                     bool in_vblank_irq, int *vpos, int *hpos,
+                                     ktime_t *stime, ktime_t *etime,
+                                     const struct drm_display_mode *mode))
+{
+	struct drm_device *dev = crtc->dev;
+	unsigned int pipe = crtc->index;
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+	struct timespec64 ts_etime, ts_vblank_time;
+	ktime_t stime, etime;
+	bool vbl_status;
+	const struct drm_display_mode *mode;
+	int vpos, hpos, i;
+	int delta_ns, duration_ns;
+
+	if (pipe >= dev->num_crtcs) {
+		DRM_ERROR("Invalid crtc %u\n", pipe);
+		return false;
+	}
+
+	/* Scanout position query not supported? Should not happen. */
+	if (!get_scanout_position) {
+		DRM_ERROR("Called from CRTC w/o get_scanout_position()!?\n");
+		return false;
+	}
+
+	if (drm_drv_uses_atomic_modeset(dev))
+		mode = &vblank->hwmode;
+	else
+		mode = &crtc->hwmode;
+
+	/* If mode timing undefined, just return as no-op:
+	 * Happens during initial modesetting of a crtc.
+	 */
+	if (mode->crtc_clock == 0) {
+		DRM_DEBUG("crtc %u: Noop due to uninitialized mode.\n", pipe);
+		WARN_ON_ONCE(drm_drv_uses_atomic_modeset(dev));
+		return false;
+	}
+
+	/* Get current scanout position with system timestamp.
+	 * Repeat query up to DRM_TIMESTAMP_MAXRETRIES times
+	 * if single query takes longer than max_error nanoseconds.
+	 *
+	 * This guarantees a tight bound on maximum error if
+	 * code gets preempted or delayed for some reason.
+	 */
+	for (i = 0; i < DRM_TIMESTAMP_MAXRETRIES; i++) {
+		/*
+		 * Get vertical and horizontal scanout position vpos, hpos,
+		 * and bounding timestamps stime, etime, pre/post query.
+		 */
+		vbl_status = get_scanout_position(crtc, in_vblank_irq, &vpos,
+						  &hpos, &stime, &etime, mode);
+
+		/* Return as no-op if scanout query unsupported or failed. */
+		if (!vbl_status) {
+			DRM_DEBUG("crtc %u : scanoutpos query failed.\n",
+				  pipe);
+			return false;
+		}
+
+		/* Compute uncertainty in timestamp of scanout position query. */
+		duration_ns = ktime_to_ns(etime) - ktime_to_ns(stime);
+
+		/* Accept result with <  max_error nsecs timing uncertainty. */
+		if (duration_ns <= *max_error)
+			break;
+	}
+
+	/* Noisy system timing? */
+	if (i == DRM_TIMESTAMP_MAXRETRIES) {
+		DRM_DEBUG("crtc %u: Noisy timestamp %d us > %d us [%d reps].\n",
+			  pipe, duration_ns/1000, *max_error/1000, i);
+	}
+
+	/* Return upper bound of timestamp precision error. */
+	*max_error = duration_ns;
+
+	/* Convert scanout position into elapsed time at raw_time query
+	 * since start of scanout at first display scanline. delta_ns
+	 * can be negative if start of scanout hasn't happened yet.
+	 */
+	delta_ns = div_s64(1000000LL * (vpos * mode->crtc_htotal + hpos),
+			   mode->crtc_clock);
+
+	/* Subtract time delta from raw timestamp to get final
+	 * vblank_time timestamp for end of vblank.
+	 */
+	*vblank_time = ktime_sub_ns(etime, delta_ns);
+
+	if (!drm_debug_enabled(DRM_UT_VBL))
+		return true;
+
+	ts_etime = ktime_to_timespec64(etime);
+	ts_vblank_time = ktime_to_timespec64(*vblank_time);
+
+	DRM_DEBUG_VBL("crtc %u : v p(%d,%d)@ %lld.%06ld -> %lld.%06ld [e %d us, %d rep]\n",
+		      pipe, hpos, vpos,
+		      (u64)ts_etime.tv_sec, ts_etime.tv_nsec / 1000,
+		      (u64)ts_vblank_time.tv_sec, ts_vblank_time.tv_nsec / 1000,
+		      duration_ns / 1000, i);
+
+	return true;
+}
+EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_internal);
+
+/**
+ * drm_crtc_vblank_helper_get_vblank_timestamp - precise vblank timestamp
+ *                                               helper
+ * @crtc: CRTC whose vblank timestamp to retrieve
+ * @max_error: Desired maximum allowable error in timestamps (nanosecs)
+ *             On return contains true maximum error of timestamp
+ * @vblank_time: Pointer to time which should receive the timestamp
+ * @in_vblank_irq:
+ *     True when called from drm_crtc_handle_vblank().  Some drivers
+ *     need to apply some workarounds for gpu-specific vblank irq quirks
+ *     if flag is set.
+ *
+ * Implements calculation of exact vblank timestamps from given drm_display_mode
+ * timings and current video scanout position of a CRTC. This can be directly
+ * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
+ * driver if &drm_crtc_helper_funcs.get_scanout_position is implemented.
+ *
+ * The current implementation only handles standard video modes. For double scan
+ * and interlaced modes the driver is supposed to adjust the hardware mode
+ * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
+ * match the scanout position reported.
+ *
+ * Note that atomic drivers must call drm_calc_timestamping_constants() before
+ * enabling a CRTC. The atomic helpers already take care of that in
+ * drm_atomic_helper_update_legacy_modeset_state().
+ *
+ * Returns:
+ *
+ * Returns true on success, and false on failure, i.e. when no accurate
+ * timestamp could be acquired.
+ */
+bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
+						 int *max_error,
+						 ktime_t *vblank_time,
+						 bool in_vblank_irq)
+{
+	return drm_crtc_vblank_helper_get_vblank_timestamp_internal(
+		crtc, max_error, vblank_time, in_vblank_irq,
+		crtc->helper_private->get_scanout_position);
+}
+EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 5e9b15a0e8c5..db46abbbf4e7 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -867,6 +867,47 @@ struct drm_crtc_funcs {
 	 * new drivers as the replacement of &drm_driver.disable_vblank hook.
 	 */
 	void (*disable_vblank)(struct drm_crtc *crtc);
+
+	/**
+	 * @get_vblank_timestamp:
+	 *
+	 * Called by drm_get_last_vbltimestamp(). Should return a precise
+	 * timestamp when the most recent vblank interval ended or will end.
+	 *
+	 * Specifically, the timestamp in @vblank_time should correspond as
+	 * closely as possible to the time when the first video scanline of
+	 * the video frame after the end of vblank will start scanning out,
+	 * the time immediately after end of the vblank interval. If the
+	 * @crtc is currently inside vblank, this will be a time in the future.
+	 * If the @crtc is currently scanning out a frame, this will be the
+	 * past start time of the current scanout. This is meant to adhere
+	 * to the OpenML OML_sync_control extension specification.
+	 *
+	 * Parameters:
+	 *
+	 * crtc:
+	 *     CRTC for which timestamp should be returned.
+	 * max_error:
+	 *     Maximum allowable timestamp error in nanoseconds.
+	 *     Implementation should strive to provide timestamp
+	 *     with an error of at most max_error nanoseconds.
+	 *     Returns true upper bound on error for timestamp.
+	 * vblank_time:
+	 *     Target location for returned vblank timestamp.
+	 * in_vblank_irq:
+	 *     True when called from drm_crtc_handle_vblank().  Some drivers
+	 *     need to apply some workarounds for gpu-specific vblank irq quirks
+	 *     if flag is set.
+	 *
+	 * Returns:
+	 *
+	 * True on success, false on failure, which means the core should
+	 * fallback to a simple timestamp taken in drm_crtc_handle_vblank().
+	 */
+	bool (*get_vblank_timestamp)(struct drm_crtc *crtc,
+				     int *max_error,
+				     ktime_t *vblank_time,
+				     bool in_vblank_irq);
 };
 
 /**
@@ -974,11 +1015,12 @@ struct drm_crtc {
 	 * Programmed mode in hw, after adjustments for encoders, crtc, panel
 	 * scaling etc. Should only be used by legacy drivers, for high
 	 * precision vblank timestamps in
-	 * drm_calc_vbltimestamp_from_scanoutpos().
+	 * drm_crtc_vblank_helper_get_vblank_timestamp().
 	 *
 	 * Note that atomic drivers should not use this, but instead use
 	 * &drm_crtc_state.adjusted_mode. And for high-precision timestamps
-	 * drm_calc_vbltimestamp_from_scanoutpos() used &drm_vblank_crtc.hwmode,
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() used
+	 * &drm_vblank_crtc.hwmode,
 	 * which is filled out by calling drm_calc_timestamping_constants().
 	 */
 	struct drm_display_mode hwmode;
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index e398512bfd5f..0afaf58da40d 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -459,8 +459,8 @@ struct drm_crtc_helper_funcs {
 	 * Returns the current display scanout position from a CRTC and an
 	 * optional accurate ktime_get() timestamp of when the position was
 	 * measured. Note that this is a helper callback which is only used
-	 * if a driver uses drm_calc_vbltimestamp_from_scanoutpos() for the
-	 * @drm_driver.get_vblank_timestamp callback.
+	 * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
+	 * for the @drm_crtc_funcs.get_vblank_timestamp callback.
 	 *
 	 * Parameters:
 	 *
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index c16c44052b3d..248fbd5de177 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -174,13 +174,13 @@ struct drm_vblank_crtc {
 	unsigned int pipe;
 	/**
 	 * @framedur_ns: Frame/Field duration in ns, used by
-	 * drm_calc_vbltimestamp_from_scanoutpos() and computed by
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() and computed by
 	 * drm_calc_timestamping_constants().
 	 */
 	int framedur_ns;
 	/**
 	 * @linedur_ns: Line duration in ns, used by
-	 * drm_calc_vbltimestamp_from_scanoutpos() and computed by
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() and computed by
 	 * drm_calc_timestamping_constants().
 	 */
 	int linedur_ns;
@@ -190,8 +190,8 @@ struct drm_vblank_crtc {
 	 *
 	 * Cache of the current hardware display mode. Only valid when @enabled
 	 * is set. This is used by helpers like
-	 * drm_calc_vbltimestamp_from_scanoutpos(). We can't just access the
-	 * hardware mode by e.g. looking at &drm_crtc_state.adjusted_mode,
+	 * drm_crtc_vblank_helper_get_vblank_timestamp(). We can't just access
+	 * the hardware mode by e.g. looking at &drm_crtc_state.adjusted_mode,
 	 * because that one is really hard to get from interrupt context.
 	 */
 	struct drm_display_mode hwmode;
@@ -238,4 +238,22 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc);
 void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
 				   u32 max_vblank_count);
+
+/*
+ * Helpers for struct drm_crtc_funcs
+ */
+
+bool
+drm_crtc_vblank_helper_get_vblank_timestamp_internal(
+	struct drm_crtc *crtc, int *max_error, ktime_t *vblank_time,
+	bool in_vblank_irq,
+	bool (*get_scanout_position)(struct drm_crtc *crtc,
+                                     bool in_vblank_irq, int *vpos, int *hpos,
+                                     ktime_t *stime, ktime_t *etime,
+                                     const struct drm_display_mode *mode));
+bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
+						 int *max_error,
+						 ktime_t *vblank_time,
+						 bool in_vblank_irq);
+
 #endif
-- 
2.24.1

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